Internally illuminated matrix



23, 1966 B. G. OLESEN ETAL 3,267,598

INTERNALLY ILLUMINATED MATRIX 2 Sheets-Sheet 1 Original Filed April 12.1960 SAFE LAUNCH LOW HiGH READY SlGNAL VOL CONTROL READY STBY @ OFF OFFSTATION BYPASS MISSILE MASTER FIG.

ATTORNEY Aug. 23, 1966 B. G. OLESEN ETAL 3,267,598

INTERNALLY ILLUMINATED MATRIX Original Filed April 12, 1960 2Sheets-Sheet z INVENTORS BOBBY G. OLESEN BARBERO DiMARTINO BY RiCHARD T.HEAP ATTORNEY United States Patent 3,267,598 INTERNALLY ILLUMINATEDMATRIX Bobby G. Olesen, Inglewood, Barbero Di Martino, Rolling Hills,Richard T. Heap, Los Alamitos, and Norman G. Haddad, Long Beach, Calif.,assignors to North American Aviation, Inc. Continuation of applicationSer. No. 21,825, Apr. 12, 1960. This application June 5, 1963, Ser. No.285,840 8 Claims. (Cl. 40-130) This is a continuation of applicationSerial No. 21,825, filed April 12, 1960, now abandoned.

This invention concerns improved means for illuminating panels uponwhich written matter or characters appear, and has particularapplication to instrument or switch consoles such as may be used inaircraft.

The invention disclosed herein is applicable to any panel or consoleinvolving written characters, letters or symbols which are read orinterpreted by an observer. However, a particular need for thisinvention arose in connection with cockpit panel illumination inadvanced high speed type aerial vehicles, wherein the greatercomplexities of the control systems and increased penalties of size andweight impose greater restrictions in the design of cockpit componentsthan in conventional aircraft.

The panel illumination system disclosed herein is within that class ofsystems which broadly comprise a light transmitting panel with a darksurface coating which is etched to expose light from within the panel inthe form of letters, symbols or other indicia, and a source of light toilluminate the panel from within. A common type of conventional controlpanel within the stated class is that comprising a sheet of acrylicresin or methylmethacrylate plastic material such as known to the tradeas Lucite or Plexiglas. With this type of material which haslight-conducting properties, it is possible to illuminate the matrix ofthe panel which then conducts light to any desired location where theindicia occurs. A source of light is provided at one or more selectedpoints within the periphery of the panel, and light from the statedsource or sources is diffused through the matrix. A dark coating isapplied over the outer surface of the panel so that light within thepanel matrix is not visible. Then portions of the covering material areout, shaved, or otherwise removed from such coating to form letters orother indicia. Where the coating is re moved, light from within thepanel matrix is emitted therefrom so that the stated indicia glows incontrast with the dark coating which forms the panel outer surfacecovering.

Among the principal advantages of the stated panel illuminationtechnique is the improved flexibility of design permitted by the factthat the sources of light used to illuminate the panel matrix may beinterspersed throughout the panel between the various knobs, switches,dials or other such items located on the panel. Since the entire panelglows internally, lettering or indicia of any type may be placedanywhere on the panel outer surface where space permits, without theneed for placing a light source directly in back of such indicia.

The advantage stated above is of particular importance in thefabrication of control panels for use in vehicles within the broad classincluding supersonic aircraft and space vehicles. In such vehicles,efiicient use of available space is of greater importance than withconventional high-performance aircraft, since the penalties of size,weight, and drag are greatly multiplied during space travel at extremelyhigh speed. Use of space at maximum efficiency requires that componentstructural parts fit together as closely as possible, with a minimum ofvoids or unused areas throughout the vehicle, including ice the cockpitarea. Therefore, it is a basic requirement in vehicles of the statedclass that the cockpit control panels be as thin and smooth as possible,permitting the closest possible relationship between such panels andadjacent structure.

Also, vehicles of the stated class are characterized by highly complexelectronic systems for performing many of the guidance and controlfunctions. Due to the increased criticality of the size and weightlimitations in supersonic vehicles as mentioned above, the compactnessand crowded internal conditions resulting from such equipment severelylimits the accessibility of items requiring adjustment or maintenancewhich may be situated out of reach within the vehicle. Therefore, it isa further requirement in vehicles of the stated class that the cockpitpanel illumination means be adapted to function without any need foradjustment or maintenance throughout the entire service life of thepanel.

In addition to the above, the increased complexity of problems incidentto operation by the pilot of vehicles within the stated class results inthe need for many additional control items in the cockpit. The switchand instrument panels in such vehicles consequently tend to be morecrowded than generally similar panels known to the prior art. Thisfactor results in less space being available for light sources,circuits, etc., used for panel illumination. Therefore, it is a furtherrequirement in such control panels that the illumination means occupy aminimum of surface area of the panel, permitting the maximumavailability of space for the controls and instruments, together withtheir identifying indicia, essential in the operation of the vehicle.

Also, due to the increased need for rapid and accurate pilot response toevery demand on his attention imposed by extremely high speed flight invehicles of the stated class, it is essential that the maximum of visualclarity and acuity be achieved by every possible means within the pilotsfield of vision. Thus, the crowding of essential controls and dialswithin the limited area of the cockpit requires careful arrangement ofthe panel so that the least possible confusion of the pilot in directinghis attention generally over the panels or selectively toward anyparticular item on a panel will result. Therefore, it is a furtherrequirement that the illumination means in panels for use in vehicles ofthe stated class be as unobtrusive as possible and preferably completelyinvisible to the pilot so that the continuity of the control orinstrument panels will not be interrupted by distractions such as bulbs,knobs, holes, or protuberances interspersed between the essential items.

Accordingly, it is a general object of the invention disclosed herein toprovide improved control panel illumination means resulting in maximumvisual clarity and acuity within the limited available panel area.

More particularly, it is a principal object of the instant invention toprovide complete illumination of a light-transmitting panel from withinby light sources which are totally invisible when the panel is viewed asduring normal use.

It is a further object of the instant invention to provide completeillumination of a panel by internal means which permit substantiallyplanar surfaces on both the front and back of the panel.

It is an additional object in this case to provide illumination of atranslucent matrix in the form of a body from within by light sourceswhich neither protrude nor are recessed below the surfaces of the body,but are in tegrally united to the body by encapsulation within thematrix.

Also, it is an object of the instant invention to provide improvedillumination means in a control panel requiring no adjustment afterinstallation, and no maintenance or replacement of light source orcircuitry during the entire service life of the panel.

It is a further object in this case to accomplish the above statedobjects by compact means having minimum weight and occupying a minimumof space.

Other objects and advantages of the instant invention will becomeapparent upon a close reading of the following detailed description ofan illustrative embodiment of the invention, reference being had to theaccompanying drawings wherein:

FIGURE 1 shows an end view of a panel constructed in accordance with theinventive principles disclosed herein,

FIGURE 2 shows a general view of a panel embodying the inventiveconcept,

FIGURE 3 shows in detailed and fragmentary form an alternative means forinstalling a light source in the panel of FIGURE 1, and

FIGURE 4 shows a View generally similar to FIGURE 3 of anotheralternative embodiment for installation of a light source.

Referring to FIGURE 1 which shows an illustrative embodiment of theinventive concept, the lighting system to be described includes a panel1 of light-transmitting matrix such as acrylic material. Embeddedtherein is a light source 2 which, for example, may comprise aminiaturized bulb such as known to the trade as a grain-ofwheat bulbcommercially available from the Chicago -Miniature Lamp Works, Chicago,Illinois. These bulbs are less than inch in length and /8 inch indiameter, and have a service life in excess of 10,000 hours, oftenexceeding 60,000 hours. Hence, such bulbs would never have to bereplaced during the life of the control panel which incorporates them.As indicated by lines, light rays from source 2 illuminate matrix 1interiorly, and are reflected between the surfaces thereof except wherelight is emitted at the exposed surface of the indicia 22.

It is axiomatic in the field of optics that the amount of lightreflected by a surface in relation to the amount which penetrates thesurface varies with changes in the angle at which light impinges uponthe surface. Each material which is capable of transmitting light has aparticular angle of incidence, called the critical angle, which is oneof the inherent light-transmitting properties of that material. All ofthe light impinging on a surface at an angle greater than the criticalangle is reflected by that surface, whereas at less angles of incidence,some of the impinging light penetrates the surface. The value of thecritical angle for each material depends upon its index of refractionand in the case of acrylic resin, the critical angle is about 45.

Because the placement of light sources 2 in a particular panel need notdepend upon the location of the indicia 22, it follows that the angle ofincidence of light rays in any particular area of the panel will varyconsiderably depending upon the relative location of such area withrespect to the light source or sources which illuminate it. Accordingly,in order to insure that a substantial portion of the light in the areaof indicia 22 will impinge at an angle less than the critical angle forthe panel material used, the panel 1 is surface treated to create agrainy or finely ground texture at the location of indicia 22, such assurface 20 in FIGURE 1. This may be accomplishedby a variety of means,one of which is to mask the panel surface by a template which exposesonly the area of the indicia, such as area 20 in FIGURE 1, andvapor-blasting such area in accordance with accepted vapor-blastingtechnique. This is done by impinging a stream of air and liquid mixedwith fine abrasive particles against the exposed area of the plasticpanel. The resulting surface roughness in the vapor-blasted area causeslight from within the panel matrix 1 to impinge on surface 20 atnumerous and diverse angles, so that a substantial portion of such lightis refracted. Thus, more light is emitted through letters or characterscomprising the indicia, causing the same to glow with improvedbrilliance in sharp contrast with the surrounding panel area.

In fabricating a control panel incorporating the improved illuminationmeans disclosed herein, after vaporblasting is accomplished as set forthabove, a layer 4 of brilliant light-reflecting material is applied tothe surface of panel matrix 1 as shown in FIGURE 1. Layer 4% maycomprise any white or silver substance, such as white enamel, oraluminum film, and which may be applied as a pre-cut sheet adhesivelyjoined to the acrylic material or may be applied by spraying, painting,dipping or other known technique. During the application of layer 4,care is required to prevent the substance of layer 4 from covering thesurface of matrix 1 where indicia such as 22 occur. Thus, surface 20 asshown in FIGURE 1 may be masked by a template, and the remaining surfaceof matrix 1 may then be coated with layer 4. Although in the drawingsonly the front surface of matrix it is coated with layer 4, it isobvious that both front and back surfaces of matrix may be similarlycoated.

Upon completion of the above step, layers 6 and 8 may be applied, eithersimultaneously or in sequence. Layer 6 may be a lightly colored or whiteplastic or white paint, applied either in sheet form with an adhesivebond or painted on by spraying, brushing or dipping. The purpose oflayer 6 is to render the indicia white or an otherwise light color, andto heighten the clarity of the indicia in contrast to the surroundingpanel surface when light from within panel matrix 1 shines through layer6. Therefore, the substance used for layer 6 should havelighttransmitting properties.

Layer 8 is a black or otherwise dark covering which may be plastic orpaint and preferably does not transfer light. Layer 8, which may beapplied as in the manner of layer 6, is allowed to become permanentlysecured to layer 6, by drying or curing, if necessary. Then thoseportions of layer 3 which lie over surfaces such as 22 in FIGURE 1wherein indicia are located are cut, shaved or otherwise removed fromlayer 8 so that layer 6 will be exposed. Thus, the indicia formed by theexposed portions of layer 6 will glow brilliantly when illuminated fromwithin panel matrix ll, while those portions of the matrix covered bylayer 8 will appear black or otherwise dark in color.

If applied simultaneously, layers 6 and 8 may be preformed plasticsheets which are placed together with a sheet of acrylic material in thedesired relationship in a mold. The face of the mold may form a diewhich will leave an impression upon the top surface of the laminae thusformed, this impression corresponding to the lettering or other indiciadesired for the finished panel. Upon the application of heat andpressure, the panel structure may be formed completely in one operation,and the black layer then cut away as described above to expose the whiteindicia beneath.

Since a panel embodying the inventive principles disclosed herein mayinclude any number of light sources 2 depending upon the particularrequirements in a given design problem, and each source is constructedin the same manner, only one need be described. As shown in FIGURE 1,the light source consists of a miniature or grain-of-wheat bulb such asheretofore described. Bulb 2 is situated within a cavity 14 which is cutor molded into the back surface of panel 1. In the structure shown byFIGURE 1, bulb 2 is embedded into cavity 14 by initially placing thebulb in the hollow of the cavity and thereafter filling the remainingvolume of the cavity with potting material or an appropriate ad hesivesuch as, for example, acrylic resin, or water white epoxy resinpreferably having the same index of refraction as panel matrix 1.

With bulb 2 thus secured as set forth above, with its two wire leads 12emerging from cavity 14, a connection between the two stated leads andan energizing circuit may be accomplished by appropriate means. Althoughthe inventive principles herein disclosed are obviously adaptable foruse with conventional wire circuits, the use of printed circuits on theback side of panel 1 results in an advantageous saving of space andweight. Accordingly, leads 12 from bulb 2 may be joined to the printedcircuit as shown in FIGURE 1.

Where metallic mirrorizing material is used for layer 4 as set forthabove, a layer of insulating material may be layed over layer 4 on theback surface of panel 1 to insulate layer 4 from the printed circuit, ifnecessary.

An alternative method of installing light bulb 2 in panel matrix 1 isshown in FIGURE 3. In this embodiment, bulb 2 is first embedded in asmall plug or cube 18 of the same material as matrix 1. A recess orcavity of shape corresponding to cube 18 is created in the back surfaceof matrix 1, and the cube with bulb 2 embedded therein may be adhesivelysecured within the stated cavity, as shown in FIGURE 3. Leads 12 frombulb 2 are soldered or otherwise joined to appropriate portions ofprinted circuit 10 as in connection with FIG- URE 1 described above.Leads 12 may be adhesively secured to panel matrix 1 within V-shapegrooves as shown in FIGURE 3, to insure that leads 12 do not protrudeabove the surface of the panel.

Instead of adhesively securing cube 18 within a corresponding recess inmatrix 1, cube 18 may be cylindrically shaped as shown in FIGURE 4 withone or more shallow helical screw threads engaging in similar threads incylindrical cavity, so that tube or plug 18, with bulb 2 embeddedtherein, may be screwed into place. At the periphery of plug 18, twonarrow spaced strips of silver conductive paint may be placed, withleads 12 from bulb 2 connected thereto. The matching recess into whichplug 18 is threadedly secured may have two similarly spaced strips ofcorresponding material connected to printed circuit 10. When plug 18 isproperly positioned as shown in FIGURE 4, the two sets of tabs are inelectrical contact, avoiding the necessity for soldered connectionbetween leads 12 and circuit 10. The alternative embodiment of FIGURE 4thus provides a means by which light sources in a panel using thisarrangement could be easily changed or replaced.

In all of the embodiments discussed above, after the installation ofillumination means disclosed herein, the panel is perfectly smooth onboth the front and back surfaces, with nothing to break the continuityof the surface. In other words, in the case of a flat panel, both thefront and the back surfaces thereof would be perfectly planar andparallel to each other. In addition, in all of the stated embodiments,one or more sources of colored light may be used in any panelincorporating the system herein disclosed by including a colored filterin the laminae forming the front surface of the finished panel.Alternatively, in the case of FIGURES 3 and 4, for example, colored ortinted plastic can be used in forming cubes or plugs 18 in which bulbs 2are embedded before the cubes are secured within matrix 1.

From the description and drawings contained herein,

it may be seen that applicants have provided an improved panelillumination system which achieves all the objectives hereinabove setforth with new and novel results. FIGURE 2 shows a general view of panelconstructed in accordance with the inventive principles disclosedherein. For purposes of illustration, the indicia are shown black inFIGURE 2 and the panel surface white, whereas in actual appearance thepanel is black or dark in tone and the indicia white. Since there are noprotrusions caused by the illumination system on the front of the panel,considerable unnecessary cluttering has been avoided and the controlsare commensurately easier to identify and operate. Removal of theprotrusions from the back of the panel increases flexibility inselecting locations for the light sources, which in turn permits moreeven panel lighting and avoidance of glare.

The structural details set forth above may obviously be varied withoutdeparting from the scope of the inventive concept as disclosed hereinand defined by the appended claims.

We claim:

1. The combination of:

a panel of transparent material in relatively thin sheet form havingindicia on an outer surface of said panel,

a light source comprising at least one electric light bulb integrallyunited to said material by encapsula tion therewithin so that the outersurface of said bulb is in substantially uniform contact with saidmaterial over substantially the entire surface of said bulb, and

means for energizing said light source to illuminate said material fromwithin.

2. The combination set forth in claim 1 above, wherein:

said panel comprises generally smooth and uninterrupted front and backsurfaces, and

said light source comprises a miniaturized bulb of a size adapted to fitbetween said surfaces whereby said surfaces are free of protrusions.

a portion of said surface of said panel is relatively coarsely texturedso that light from within said material is ditfused and refractedthrough said portion at a multitude of different refraction angles.

4. The combination set forth in claim 3 above, having in additionthereto:

a coating of opaque material completely covering said panel except whereportions of said opaque material are lacking in areas which form saidindicia through which light from within said matrix passing through saidrelatively coarse surface portion also passes.

5. The method of installing a source of light in a relativelythin-walled panel of transparent material comprising the steps of:

providing a hollow cavity in one surface of said panel,

placing a relatively small light bulb in said cavity,

filling said cavity with a fluid capable of hardening into a transparentsolid material, and

hardening said fluid whereby said bulb is integrally joined to saidtransparent material and securely supported in stationary relationshipin relation to said panel.

6. The combination set forth in claim 1 above, wheresaid panel has aback surface having a cavity located therein,

said material in which said electric lightbulb is encapsulated is a cubebeing of a shape corresponding with the shape of said cavity so as tocompletely fill the same,

said cube being secured within said cavity so that the exposed surfaceof said cube is flush with said back surface of said panel, presenting asmooth, uninterrupted surface throughout said panel, and

means for securing said cube within said cavity.

7. The combination set forth in claim 6 above, wheresaid cube of saidmaterial is tinted with color so that the illumination originating fromsaid light source assumes the color of said tinting.

8. The combination set forth in claim 1 above, wheresaid panel has aback surface having a generally cylindrical shaped cavity locatedtherein,

said material in which said electric lightbulb is encapsulated is agenerally cylindrical plug of said material,

3. The combination set forth in claim 2 above, Where- I 2,795,069 7/1957Hardesty 40130 H. ROSS, Assistant Examiner.

7 8 said plug being of a shape corresponding with the shape 2,808,528/1957 Martin 40130 X of said cavity soas to Completely fill the same,2,821,800 2/1958 Hardesty 40-130 said plug further having a helicalthread on the gen- 24, 99 2/1958 Nellgass 40-130 eraliy cylindricalsurface of said plug, 31 1 1 7/ 1953 Hardest}! gg said cavity having ahelical thread o its generally 5 -1832:877 9/1958 Goebel cylindricalSurface, and 2,864,057 12/1958 Connelly 2 0121 sai plug being adapted tofi-t within said cavity by in- E2332 8: terengagement of said twohelical threads on said 3018614 1/1962 Brien Y X 7 Plug and Sendrespectlvely- 10 3,059,134 10/1962 Tedrick 4o 13o X Reierences Cited bythe Examiner 2/1964 Nuenz 40-130 X K UNITED STATES PATENTS PATENTS1,995,863 3/1935 Prideaux 40-130 X 3361764 4/1959 swltzerltmd- 211705008/1939 W11 40-130 X 15 EUGENE R. CAPOZIO, Primary Examiner, 2,337,74412/1943 Garstang 40-130 X 2,651,864 9/1953 HoWenstine 40 130 JEROMESCHNALL, Examiner-

1. THE COMBINATION OF: A PANEL OF TRANSPARENT MATERIAL IN RELATIVELYTHIN SHEET FORM HAVING INDICIA ON AN OUTER SURFACE OF SAID PANEL, ALIGHT SOURCE COMPRISING AT LEAST ONE ELECTRIC LIGHT BULB INTEGRALLYUNITED TO SAID MATERIAL BY ENCAPSULATION THEREWITHIN SO THAT THE OUTERSURFACE OF SAID BULB IS IN SUBSTANTIALLY UNIFORM CONTACT WITH SAIDMATERIAL OVER SUBSTANTIALLY THE ENTIRE SURFACE OF SAID BULB, AND MEANSFOR ENERGIZING SAID LIGHT SOURCE TO ILLUMINATE SAID MATERIAL FROMWITHIN.